Research On Continuous-variable Source-independent Quantum Random Number Generator

Quantum random number generator exploits the intrinsic randomness of quantum random processes to generate random numbers,which enables the generation of true random numbers theoretically.The continuous-variable quan-tum random number generator based on measuring vacuum fluctuation,which has the advantages of high random number generation rate,low system com-plexity,and easy integration realization,performs outstanding superiority in system industrialization and it has become the research hotspot in the field of random number generation.Recently,research on the continuous-variable quantum random number generator based on measuring vacuum fluctuation has made continuous breakthroughs in system implementation,moving from the platform systems to chip-level demonstrations,and gradually exploring and developing its practical applications.However,the quantum random number generator constructed by practi-cal imperfect devices inevitably has security vulnerabilities and it is extremely necessary to model and analyze the constructed devices to avoid their effects.In particular,the random source,which acts as the most complex module in the system,is difficult for the users to perfectly model in advance or moni-tor whether it is controlled by an eavesdropper.To overcome this challenge,the continuous-variable source-independent quantum random number genera-tor protocol can relax the security requirements of the source device by trusting the detection system,thereby ensuring the generation of secure random num-bers under the condition that the source device is not trusted.Currently,the research of continuous-variable source-independent quantum random number generator focuses on the schemes of measuring vacuum fluctuation based on ho-modyne detection or heterodyne detection,where the homodyne-based scheme has received more attention in recent years due to its simpler structure.It is worth noting that due to the late start of research on continuous-variable source-independent quantum random number generator systems,exist-ing experimental systems have focused on proposing new protocols and rarely considered the practical security of these protocols,so it is difficult to promote them directly.In fact,the security problem introduced by the practical imper-fections of the system is a subject that needs to be analyzed and solved urgently.Simultaneously,how to improve the real-time random number generation rate is also extremely important under the premise of ensuring security.This article focuses on increasing the random number generation rate,the practical security analysis and the system structure optimization of a continuous-variable source-independent quantum random number generator under actual conditions,and the following researches are included.1.A random extraction algorithm suitable for all quantum random number generators is proposed,which enables the realization of high-speed ran-dom extraction under the condition of limited computing resources by optimizing the implementation algorithm of the Toeplitz hashing extrac-tor and effectively alleviates the rate bottleneck problem faced by current quantum random number generators when they are extended to practical applications.Although the Toeplitz hashing extractor is a proven random extractor with low complexity and provable security,its random extrac-tion rate is limited by its implementation complexity,extraction matrix size,performance of computing platform and other factors.Due to the field programmable gate array platform is characterized by limited com-puting resources,low operating frequency and parallel computing,here a pipelined multi-module collaborative computing algorithm is designed.Simultaneously,inside each arithmetic module,exclusive OR operations between the columns of matrix is performed according to the character-istics of the Toeplitz matrix,which significantly reduces the system im-plementation complexity and improves the random extraction rate under limited computing resources and limited operating frequency.Through experiments,it is further verified that the optimized algorithm supports high-speed and secure random extraction.2.Two practical security loopholes encountered by a continuous-variable source-independent quantum random number generator based on homo-dyne detection are analyzed,including the intensity fluctuation problem of local oscillator and the finite sampling range problem of analog-to-digital converter.By analyzing the impacts of these two security loopholes on the security of continuous-variable source-independent quantum random number generators,an eavesdropping attack method by exploiting the lo-cal oscillator intensity fluctuation is proposed.Furthermore,we amend the existing random number generation rate evaluation formula based on the entropy uncertainty relationship,taking the possible sampling satura-tion into account in the security analysis of the system.Finally,quanti-tative analysis and verification of the above-mentioned two loopholes on the security of a practical continuous-variable source-independent quan-tum random number generator are verified through theoretical analysis and numerical simulations.3.A bias-free continuous-variable source-independent quantum random num-ber generator scheme is proposed.In a practical asymmetric system,there inevitably exists an offset in the measured signals,which will obviously inhibit the supportable local oscillator intensity and thus compromise the system's random number generation rate.Simultaneously,the residual common-mode noise remained in the output signals poses a potential threat to the security of generated random numbers.Aiming at the offset prob-lem in the practical asymmetric detection system,here we propose an all-optical scheme to achieve offset cancellation,where it is further applied to realize the bias-free continuous-variable source-independent quantum random number generator system.By optimizing the system parameters,the scheme can not only avoid the system measuring multiple orthogonal quadratures in each measurement,but also provide support for the research of the influences of equal and unequal orthogonal quadratures on the per-formance of source-independent quantum random number generator.At the same time,this scheme provides a feasible solution for the chip in-tegration of a continuous-variable source-independent quantum random number generator system.